192 research outputs found
Oberflaechenuntersuchungen an Niob fuer supraleitende Resonatoren mittels der Roentgen-Photoelektronenspektroskopie und der Auger-Elektronenspektroskopie
Selenoprofiles: profile-based scanning of eukaryotic genome sequences for selenoprotein genes
Motivation: Selenoproteins are a group of proteins that contain selenocysteine (Sec), a rare amino acid inserted co-translationally into the protein chain. The Sec codon is UGA, which is normally a stop codon. In selenoproteins, UGA is recoded to Sec in presence of specific features on selenoprotein gene transcripts. Due to the dual role of the UGA codon, selenoprotein prediction and annotation are difficult tasks, and even known selenoproteins are often misannotated in genome databases
Identification of Widespread Adenosine Nucleotide Binding in Mycobacterium tuberculosis
SummaryComputational prediction of protein function is frequently error-prone and incomplete. In Mycobacterium tuberculosis (Mtb), ā¼25% of all genes have no predicted function and are annotated as hypothetical proteins, severely limiting our understanding of Mtb pathogenicity. Here, we utilize a high-throughput quantitative activity-based protein profiling (ABPP) platform to probe, annotate, and validate ATP-binding proteins in Mtb. We experimentally validate prior inĀ silico predictions of >240 proteins and identify 72 hypothetical proteins as ATP binders. ATP interacts with proteins with diverse and unrelated sequences, providing an expanded view of adenosine nucleotide binding in Mtb. Several hypothetical ATP binders are essential or taxonomically limited, suggesting specialized functions in mycobacterial physiology and pathogenicity
Quantitative and Qualitative Analyses of the Cell Death Process in Candida albicans Treated by Antifungal Agents
The death process of Candida albicans was investigated after treatment with the antifungal agents flucytosine and amphotericin B by assessing morphological and biophysical properties associated with cell death. C. albicans was treated varying time periods (from 6 to 48 hours) and examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM and AFM images clearly showed changes in morphology and biophysical properties. After drug treatment, the membrane of C. albicans was perforated, deformed, and shrunken. Compared to the control, C. albicans treated with flucytosine was softer and initially showed a greater adhesive force. Conversely, C. albicans treated with amphotericin B was harder and had a lower adhesive force. In both cases, the surface roughness increased as the treatment time increased. The relationships between morphological changes and the drugs were observed by AFM clearly; the surface of C. albicans treated with flucytosine underwent membrane collapse, expansion of holes, and shrinkage, while the membranes of cells treated with amphotericin B peeled off. According to these observations, the death process of C. albicans was divided into 4 phases, CDP0, CDP1, CDP2, and CDP4, which were determined based on morphological changes. Our results could be employed to further investigate the antifungal activity of compounds derived from natural sources
Ex vivo correction of selenoprotein N deficiency in rigid spine muscular dystrophy caused by a mutation in the selenocysteine codon
Premature termination of translation due to nonsense mutations is a frequent cause of inherited diseases. Therefore, many efforts were invested in the development of strategies or compounds to selectively suppress this default. Selenoproteins are interesting candidates considering the idiosyncrasy of the amino acid selenocysteine (Sec) insertion mechanism. Here, we focused our studies on SEPN1, a selenoprotein gene whose mutations entail genetic disorders resulting in different forms of muscular diseases. Selective correction of a nonsense mutation at the Sec codon (UGA to UAA) was undertaken with a corrector tRNASec that was engineered to harbor a compensatory mutation in the anticodon. We demonstrated that its expression restored synthesis of a full-length selenoprotein N both in HeLa cells and in skin fibroblasts from a patient carrying the mutated Sec codon. Readthrough of the UAA codon was effectively dependent on the Sec insertion machinery, therefore being highly selective for this gene and unlikely to generate off-target effects. In addition, we observed that expression of the corrector tRNASec stabilized the mutated SEPN1 transcript that was otherwise more subject to degradation. In conclusion, our data provide interesting evidence that premature termination of translation due to nonsense mutations is amenable to correction, in the context of the specialized selenoprotein synthesis mechanism
Identification of a signature motif for the eIF4a3āSECIS interaction
eIF4a3, a DEAD-box protein family member, is a component of the exon junction complex which assembles on spliced mRNAs. The protein also acts as a transcript-selective translational repressor of selenoprotein synthesis during selenium deficiency. Selenocysteine (Sec) incorporation into selenoproteins requires a Sec Insertion Sequence (SECIS) element in the 3ā² untranslated region. During selenium deficiency, eIF4a3 binds SECIS elements from non-essential selenoproteins, preventing Sec insertion. We identified a molecular signature for the eIF4a3-SECIS interaction using RNA gel shifts, surface plasmon resonance and enzymatic foot printing. Our results support a two-site interaction model, where eIF4a3 binds the internal and apical loops of the SECIS. Additionally, the stability of the complex requires uridine in the SECIS core. In terms of protein requirements, the two globular domains of eIF4a3, which are connected by a linker, are both critical for SECIS binding. Compared to full-length eIF4a3, the two domains in trans bind with a lower association rate but notably, the uridine is no longer important for complex stability. These results provide insight into how eIF4a3 discriminates among SECIS elements and represses translation
Tungsten-niobium oxide bronzes: a bulk and surface structural study
[EN] Materials from the WO3-Nb2O5 system, presenting bronze-type crystal structures, display outstanding functional properties for several applications as thermoelectric materials, lithium-ion battery electrodes, or catalysts. In this work, a series of W-Nb-O oxide bronzes have been synthesized by the hydrothermal method (with Nb/(W + Nb) ratios in the range of 0-1). A combination of bulk and surface characterisation techniques has been applied to get further insights into: (i) the effect of thermal treatments on as-prepared materials and (ii) the surface chemical nature of W-Nb-O oxide bronzes. Thermal treatments promote the following structural changes: (i) loss of emerging long-range order and (ii) the elimination of NH4+ and H2O species from the structural channels of the as-synthesized materials. It has been observed that W-Nb-O bronzes with Nb at% of ca. 50% are able to retain a long-range order after heat-treatments, which is attributed to the presence of a Cs-0.5[W2.5Nb2.5O14]-type structure. Increasing amounts of Nb 5T in the materials (i) promote a phase transition to pseudocrystalline phases ordered along the c-axis; (ii) stabilize surface W s. species (elucidated by XPS); and (iii) increase the proportion of surface Lewis acid sites (as determined by the FTIR of adsorbed CO). Results suggest that pseudocrystalline oxides (with a Nb at% >= 50%) are closely related to NbO2 pentagonal bipyramid-containing structures. The stabilisation of Lewis acid sites on these pseudocrystalline materials leads to a higher yield of heavy compounds, at the expense of acrolein formation, in the gas-phase dehydration of glycerol.The authors would like to acknowledge the Ministerio de Ciencia, Innovacion y Universidades in Spain for the financial support (RTI2018-099668-B-C21 and SEV-2016-0683 projects), and the Electron Microscopy Service at Universitat Politecnica de Valencia for providing facilities and technical support. D. D. also thanks Severo Ochoa Excellence Program for his fellowship (SVP-2014-068669).Delgado-MuƱoz, D.; ConcepciĆ³n Heydorn, P.; Trunschke, A.; LĆ³pez Nieto, JM. (2020). Tungsten-niobium oxide bronzes: a bulk and surface structural study. Dalton Transactions. 49(38):13282-13293. https://doi.org/10.1039/d0dt02058cS13282132934938D. J. M. Bevan and P.Hagenmuller , Non-Stoichiometric Compounds , Pergamon , 1973Quan, H., Gao, Y., & Wang, W. (2020). Tungsten oxide-based visible light-driven photocatalysts: crystal and electronic structures and strategies for photocatalytic efficiency enhancement. Inorganic Chemistry Frontiers, 7(4), 817-838. doi:10.1039/c9qi01516gWu, C.-M., Naseem, S., Chou, M.-H., Wang, J.-H., & Jian, Y.-Q. (2019). Recent Advances in Tungsten-Oxide-Based Materials and Their Applications. Frontiers in Materials, 6. doi:10.3389/fmats.2019.00049P. G. Dickens and M. F.Pye , in Intercalation Chemistry , ed. M. S. Whittingham and A. J. Jacobson , Academic Press , 1982 , pp. 539ā561Tilley, R. J. D. (1995). The crystal chemistry of the higher tungsten oxides. International Journal of Refractory Metals and Hard Materials, 13(1-3), 93-109. doi:10.1016/0263-4368(95)00004-6CHEETHAM, A. K., & VON DREELE, R. B. (1973). Cation Distributions in Niobium Oxide Block Structures. Nature Physical Science, 244(139), 139-140. doi:10.1038/physci244139a0Obayashi, H., & Anderson, J. S. (1976). Intermediate phases and pseudophases in the system WO3Nb2O5: Tetragonal tungsten bronze phases. Journal of Solid State Chemistry, 17(1-2), 79-89. doi:10.1016/0022-4596(76)90205-xMAGNĆLI, A. (1950). Structure of Ī²-Tungsten Oxide. Nature, 165(4192), 356-357. doi:10.1038/165356b0M. Greenblatt , in Physics and Chemistry of Low-Dimensional Inorganic Conductors , ed. C. Schlenker , J. Dumas , M. Greenblatt and S. van Smaalen , Springer US , Boston, MA , 1996 , vol. 2 , pp. 15ā43Chen, J., Wang, H., Deng, J., Xu, C., & Wang, Y. (2018). Low-crystalline tungsten trioxide anode with superior electrochemical performance for flexible solid-state asymmetry supercapacitor. Journal of Materials Chemistry A, 6(19), 8986-8991. doi:10.1039/c8ta01323cGarcĆa-GonzĆ”lez, E., Soriano, M. D., Urones-Garrote, E., & LĆ³pez Nieto, J. M. (2014). On the origin of the spontaneous formation of nanocavities in hexagonal bronzes (W,V)O3. Dalton Trans., 43(39), 14644-14652. doi:10.1039/c4dt01465kSoriano, M. D., ConcepciĆ³n, P., Nieto, J. M. L., Cavani, F., Guidetti, S., & Trevisanut, C. (2011). Tungsten-Vanadium mixed oxides for the oxidehydration of glycerol into acrylic acid. Green Chemistry, 13(10), 2954. doi:10.1039/c1gc15622eMurayama, T., Kuramata, N., Takatama, S., Nakatani, K., Izumi, S., Yi, X., & Ueda, W. (2012). Synthesis of porous and acidic complex metal oxide catalyst based on group 5 and 6 elements. Catalysis Today, 185(1), 224-229. doi:10.1016/j.cattod.2011.10.029Omata, K., Izumi, S., Murayama, T., & Ueda, W. (2013). Hydrothermal synthesis of WāNb complex metal oxides and their application to catalytic dehydration of glycerol to acrolein. Catalysis Today, 201, 7-11. doi:10.1016/j.cattod.2012.06.004Thibodeau, T. J., Canney, A. S., DeSisto, W. J., Wheeler, M. C., Amar, F. G., & Frederick, B. G. (2010). Composition of tungsten oxide bronzes active for hydrodeoxygenation. Applied Catalysis A: General, 388(1-2), 86-95. doi:10.1016/j.apcata.2010.08.025M. J. Sienko , in Nonstoichiometric Compounds, Advances in Chemistry , ed. R. Ward , American Chemical Society , 1963 , vol. 39 , ch. 21, pp. 224ā236Yang, C., Chen, J.-F., Zeng, X., Cheng, D., & Cao, D. (2014). Design of the Alkali-Metal-Doped WO3 as a Near-Infrared Shielding Material for Smart Window. Industrial & Engineering Chemistry Research, 53(46), 17981-17988. doi:10.1021/ie503284xMigas, D. B., Shaposhnikov, V. L., Rodin, V. N., & Borisenko, V. E. (2010). Tungsten oxides. I. Effects of oxygen vacancies and doping on electronic and optical properties of different phases of WO3. Journal of Applied Physics, 108(9), 093713. doi:10.1063/1.3505688Ostertag, W., & Collins, C. V. (1967). Electrical resistivity of cubic rare earth, thorium and uranium tungsten bronzes. Materials Research Bulletin, 2(2), 217-221. doi:10.1016/0025-5408(67)90060-8Ostertag, W. (1966). Rare Earth Tungsten Bronzes. Inorganic Chemistry, 5(5), 758-760. doi:10.1021/ic50039a014Von Rohr, F. O., Ryser, A., Ji, H., Stolze, K., Tao, J., Frick, J. J., ā¦ Cava, R. J. (2019). The
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Oxygen Excess Antimony Tungsten Bronze. Chemistry ā A European Journal, 25(8), 2082-2088. doi:10.1002/chem.201805251Cerretti, G., Schrade, M., Song, X., Balke, B., Lu, H., Weidner, T., ā¦ Tremel, W. (2017). Thermal stability and enhanced thermoelectric properties of the tetragonal tungsten bronzes Nb8āxW9+xO47 (0 < x < 5). Journal of Materials Chemistry A, 5(20), 9768-9774. doi:10.1039/c7ta01121kGriffith, K. J., Wiaderek, K. M., Cibin, G., Marbella, L. E., & Grey, C. P. (2018). Niobium tungsten oxides for high-rate lithium-ion energy storage. Nature, 559(7715), 556-563. doi:10.1038/s41586-018-0347-0Okumura, K., Tomiyama, T., Shirakawa, S., Ishida, S., Sanada, T., Arao, M., & Niwa, M. (2011). Hydrothermal synthesis and catalysis of Nb2O5āWOxnanofiber crystal. J. Mater. Chem., 21(1), 229-235. doi:10.1039/c0jm02882gDelgado, D., FernĆ”ndez-Arroyo, A., Domine, M. E., GarcĆa-GonzĆ”lez, E., & LĆ³pez Nieto, J. M. (2019). WāNbāO oxides with tunable acid properties as efficient catalysts for the transformation of biomass-derived oxygenates in aqueous systems. Catalysis Science & Technology, 9(12), 3126-3136. doi:10.1039/c9cy00367cSaha, D., Jensen, K. M. Ć., Tyrsted, C., BĆøjesen, E. D., Mamakhel, A. H., Dippel, A.-C., ā¦ Iversen, B. B. (2014). In Situ Total X-Ray Scattering Study of WO3Nanoparticle Formation under Hydrothermal Conditions. Angewandte Chemie International Edition, 53(14), 3667-3670. doi:10.1002/anie.201311254Juelsholt, M., Lindahl Christiansen, T., & Jensen, K. M. Ć. (2019). Mechanisms for Tungsten Oxide Nanoparticle Formation in Solvothermal Synthesis: From Polyoxometalates to Crystalline Materials. The Journal of Physical Chemistry C, 123(8), 5110-5119. doi:10.1021/acs.jpcc.8b12395Murayama, T., Kuramata, N., & Ueda, W. (2016). Hydrothermal synthesis of WāTaāO complex metal oxides by assembling MO6 (M = W or Ta) octahedra and creation of solid acid. Journal of Catalysis, 339, 143-152. doi:10.1016/j.jcat.2016.04.007Murayama, T., Nakajima, K., Hirata, J., Omata, K., Hensen, E. J. M., & Ueda, W. (2017). Hydrothermal synthesis of a layered-type WāTiāO mixed metal oxide and its solid acid activity. Catalysis Science & Technology, 7(1), 243-250. doi:10.1039/c6cy02198kDelgado, D., Soriano, M. D., Solsona, B., Zamora, S., Agouram, S., ConcepciĆ³n, P., & LĆ³pez Nieto, J. M. (2019). Tungsten-titanium mixed oxide bronzes: Synthesis, characterization and catalytic behavior in methanol transformation. Applied Catalysis A: General, 582, 117092. doi:10.1016/j.apcata.2019.05.026Delgado, D., Chieregato, A., Soriano, M. D., RodrĆguez-Aguado, E., Ruiz-RodrĆguez, L., RodrĆguez-CastellĆ³n, E., & LĆ³pez Nieto, J. M. (2018). Influence of Phase Composition of Bulk Tungsten Vanadium Oxides on the Aerobic Transformation of Methanol and Glycerol. European Journal of Inorganic Chemistry, 2018(10), 1204-1211. doi:10.1002/ejic.201800059Delgado, D., FernĆ”ndez-Arroyo, A., Salvia, N. L., Domine, M. E., & Nieto, J. M. L. (2019). Reflux-synthesized bulk and diluted W-Nb-O mixed oxide bronzes for the valorization of short-chain oxygenates aqueous mixtures. Chinese Journal of Catalysis, 40(11), 1778-1787. doi:10.1016/s1872-2067(19)63419-4La Salvia, N., Delgado, D., Ruiz-RodrĆguez, L., Nadji, L., MassĆ³, A., & Nieto, J. M. L. (2017). V- and Nb-containing tungsten bronzes catalysts for the aerobic transformation of ethanol and glycerol. Bulk and supported materials. Catalysis Today, 296, 2-9. doi:10.1016/j.cattod.2017.04.009Choi, J., Moon, K., Kang, I., Kim, S., Yoo, P. J., Oh, K. W., & Park, J. (2015). Preparation of quaternary tungsten bronze nanoparticles by a thermal decomposition of ammonium metatungstate with oleylamine. Chemical Engineering Journal, 281, 236-242. doi:10.1016/j.cej.2015.06.101Nieto, J. M. L., Botella, P., VĆ”zquez, M. I., & Dejoz, A. (2002). The selective oxidative dehydrogenation of ethane over hydrothermally synthesised MoVTeNb catalysts. Chem. Commun., (17), 1906-1907. doi:10.1039/b204037aSadakane, M., Yamagata, K., Kodato, K., Endo, K., Toriumi, K., Ozawa, Y., ā¦ Ueda, W. (2009). Synthesis of Orthorhombic Mo-V-Sb Oxide Species by Assembly of Pentagonal Mo6O21Polyoxometalate Building Blocks. Angewandte Chemie International Edition, 48(21), 3782-3786. doi:10.1002/anie.200805792Wagner, J. B., Timpe, O., Hamid, F. A., Trunschke, A., Wild, U., Su, D. S., ā¦ Schlƶgl, R. (2006). Surface texturing of MoāVāTeāNbāO x selective oxidation catalysts. Topics in Catalysis, 38(1-3), 51-58. doi:10.1007/s11244-006-0070-1Barthel, J., Weirich, T. E., Cox, G., Hibst, H., & Thust, A. (2010). Structure of Cs0.5[Nb2.5W2.5O14] analysed by focal-series reconstruction and crystallographic image processing. Acta Materialia, 58(10), 3764-3772. doi:10.1016/j.actamat.2010.03.016Soriano, M. D., GarcĆa-GonzĆ”lez, E., ConcepciĆ³n, P., Rodella, C. B., & LĆ³pez Nieto, J. M. (2017). Self-Organized Transformation from Hexagonal to Orthorhombic Bronze of CsāNbāWāO Mixed Oxides Prepared Hydrothermally. Crystal Growth & Design, 17(12), 6320-6331. doi:10.1021/acs.cgd.7b00999Dickens, P. G., & Whittingham, M. S. (1968). The tungsten bronzes and related compounds. Quarterly Reviews, Chemical Society, 22(1), 30. doi:10.1039/qr9682200030MAGNĆLI, A. (1952). Tungsten Bronzes containing Six-membered Rings of WO6 Octahedra. Nature, 169(4306), 791-792. doi:10.1038/169791a0SzilĆ”gyi, I. M., MadarĆ”sz, J., Pokol, G., KirĆ”ly, P., TĆ”rkĆ”nyi, G., Saukko, S., ā¦ Varga-Josepovits, K. (2008). Stability and Controlled Composition of Hexagonal WO3. Chemistry of Materials, 20(12), 4116-4125. doi:10.1021/cm800668xPinar, A. B., MĆ”rquez-Ćlvarez, C., Grande-Casas, M., & PĆ©rez-Pariente, J. (2009). Template-controlled acidity and catalytic activity of ferrierite crystals. Journal of Catalysis, 263(2), 258-265. doi:10.1016/j.jcat.2009.02.017Gu, Z., Ma, Y., Zhai, T., Gao, B., Yang, W., & Yao, J. (2006). A Simple Hydrothermal Method for the Large-Scale Synthesis of Single-Crystal Potassium Tungsten Bronze Nanowires. Chemistry - A European Journal, 12(29), 7717-7723. doi:10.1002/chem.200600077Xie, F. Y., Gong, L., Liu, X., Tao, Y. T., Zhang, W. H., Chen, S. H., ā¦ Chen, J. (2012). XPS studies on surface reduction of tungsten oxide nanowire film by Ar+ bombardment. Journal of Electron Spectroscopy and Related Phenomena, 185(3-4), 112-118. doi:10.1016/j.elspec.2012.01.004Grundner, M., & Halbritter, J. (1980). XPS and AES studies on oxide growth and oxide coatings on niobium. Journal of Applied Physics, 51(1), 397-405. doi:10.1063/1.327386Kreissl, H. T., Li, M. M. J., Peng, Y.-K., Nakagawa, K., Hooper, T. J. N., Hanna, J. V., ā¦ Tsang, S. C. E. (2017). Structural Studies of Bulk to Nanosize Niobium Oxides with Correlation to Their Acidity. Journal of the American Chemical Society, 139(36), 12670-12680. doi:10.1021/jacs.7b06856BURSILL, L. A., & HYDE, B. G. (1972). Rotation Faults in Crystals. Nature Physical Science, 240(102), 122-124. doi:10.1038/physci240122a0Bursill, L. A., & Smith, D. J. (1984). Interaction of small and extended defects in nonstoichiometric oxides. Nature, 309(5966), 319-321. doi:10.1038/309319a0Migas, D. B., Shaposhnikov, V. L., & Borisenko, V. E. (2010). Tungsten oxides. II. The metallic nature of MagnĆ©li phases. Journal of Applied Physics, 108(9), 093714. doi:10.1063/1.3505689Dupin, J.-C., Gonbeau, D., Vinatier, P., & Levasseur, A. (2000). Systematic XPS studies of metal oxides, hydroxides and peroxides. Physical Chemistry Chemical Physics, 2(6), 1319-1324. doi:10.1039/a908800hCiftyĆ¼rek, E., Å mĆd, B., Li, Z., MatolĆn, V., & Schierbaum, K. (2019). Spectroscopic Understanding of SnO2 and WO3 Metal Oxide Surfaces with Advanced Synchrotron Based; XPS-UPS and Near Ambient Pressure (NAP) XPS Surface Sensitive Techniques for Gas Sensor Applications under Operational Conditions. Sensors, 19(21), 4737. doi:10.3390/s19214737Pawlak, D. A., Ito, M., Oku, M., Shimamura, K., & Fukuda, T. (2001). Interpretation of XPS O (1s) in Mixed Oxides Proved on Mixed Perovskite Crystals. The Journal of Physical Chemistry B, 106(2), 504-507. doi:10.1021/jp012040aA. Davydov , Molecular Spectroscopy of Oxide Catalyst Surfaces , John Wiley & Sons , Hoboken , 2003 , pp. 27ā179Perra, D., Drenchev, N., Chakarova, K., Cutrufello, M. G., & Hadjiivanov, K. (2014). Remarkable acid strength of ammonium ions in zeolites: FTIR study of low-temperature CO adsorption on NH4FER. RSC Adv., 4(99), 56183-56187. doi:10.1039/c4ra12504eZecchina, A., Marchese, L., Bordiga, S., PazĆØ, C., & Gianotti, E. (1997). Vibrational Spectroscopy of NH4+ Ions in Zeolitic Materials:ā An IR Study. The Journal of Physical Chemistry B, 101(48), 10128-10135. doi:10.1021/jp9717554Katryniok, B., Paul, S., BelliĆØre-Baca, V., Rey, P., & Dumeignil, F. (2010). Glycerol dehydration to acrolein in the context of new uses of glycerol. Green Chemistry, 12(12), 2079. doi:10.1039/c0gc00307gFoo, G. S., Wei, D., Sholl, D. S., & Sievers, C. (2014). Role of Lewis and BrĆønsted Acid Sites in the Dehydration of Glycerol over Niobia. ACS Catalysis, 4(9), 3180-3192. doi:10.1021/cs5006376Sung, K.-H., & Cheng, S. (2017). Effect of Nb doping in WO3/ZrO2 catalysts on gas phase dehydration of glycerol to form acrolein. RSC Advances, 7(66), 41880-41888. doi:10.1039/c7ra08154
Novel Role of Phosphorylation-Dependent Interaction between FtsZ and FipA in Mycobacterial Cell Division
The bacterial divisome is a multiprotein complex. Specific protein-protein interactions specify whether cell division occurs optimally, or whether division is arrested. Little is known about these protein-protein interactions and their regulation in mycobacteria. We have investigated the interrelationship between the products of the Mycobacterium tuberculosis gene cluster Rv0014c-Rv0019c, namely PknA (encoded by Rv0014c) and FtsZ-interacting protein A, FipA (encoded by Rv0019c) and the products of the division cell wall (dcw) cluster, namely FtsZ and FtsQ. M. smegmatis strains depleted in components of the two gene clusters have been complemented with orthologs of the respective genes of M. tuberculosis. Here we identify FipA as an interacting partner of FtsZ and FtsQ and establish that PknA-dependent phosphorylation of FipA on T77 and FtsZ on T343 is required for cell division under oxidative stress. A fipA knockout strain of M. smegmatis is less capable of withstanding oxidative stress than the wild type and showed elongation of cells due to a defect in septum formation. Localization of FtsQ, FtsZ and FipA at mid-cell was also compromised. Growth and survival defects under oxidative stress could be functionally complemented by fipA of M. tuberculosis but not its T77A mutant. Merodiploid strains of M. smegmatis expressing the FtsZ(T343A) showed inhibition of FtsZ-FipA interaction and Z ring formation under oxidative stress. Knockdown of FipA led to elongation of M. tuberculosis cells grown in macrophages and reduced intramacrophage growth. These data reveal a novel role of phosphorylation-dependent protein-protein interactions involving FipA, in the sustenance of mycobacterial cell division under oxidative stress
Novel structural determinants in human SECIS elements modulate the translational recoding of UGA as selenocysteine
The selenocysteine insertion sequence (SECIS) element directs the translational recoding of UGA as selenocysteine. In eukaryotes, the SECIS is located downstream of the UGA codon in the 3ā²-UTR of the selenoprotein mRNA. Despite poor sequence conservation, all SECIS elements form a similar stem-loop structure containing a putative kink-turn motif. We functionally characterized the 26 SECIS elements encoded in the human genome. Surprisingly, the SECIS elements displayed a wide range of UGA recoding activities, spanning several 1000-fold in vivo and several 100-fold in vitro. The difference in activity between a representative strong and weak SECIS element was not explained by differential binding affinity of SECIS binding Protein 2, a limiting factor for selenocysteine incorporation. Using chimeric SECIS molecules, we identified the internal loop and helix 2, which flank the kink-turn motif, as critical determinants of UGA recoding activity. The simultaneous presence of a GC base pair in helix 2 and a U in the 5ā²-side of the internal loop was a statistically significant predictor of weak recoding activity. Thus, the SECIS contains intrinsic information that modulates selenocysteine incorporation efficiency
A Limited Number of Antibody Specificities Mediate Broad and Potent Serum Neutralization in Selected HIV-1 Infected Individuals
A protective vaccine against HIV-1 will likely require the elicitation of a broadly neutralizing antibody (bNAb) response. Although the development of an immunogen that elicits such antibodies remains elusive, a proportion of HIV-1 infected individuals evolve broadly neutralizing serum responses over time, demonstrating that the human immune system can recognize and generate NAbs to conserved epitopes on the virus. Understanding the specificities that mediate broad neutralization will provide insight into which epitopes should be targeted for immunogen design and aid in the isolation of broadly neutralizing monoclonal antibodies from these donors. Here, we have used a number of new and established technologies to map the bNAb specificities in the sera of 19 donors who exhibit among the most potent cross-clade serum neutralizing activities observed to date. The results suggest that broad and potent serum neutralization arises in most donors through a limited number of specificities (1ā2 per donor). The major targets recognized are an epitope defined by the bNAbs PG9 and PG16 that is associated with conserved regions of the V1, V2 and V3 loops, an epitope overlapping the CD4 binding site and possibly the coreceptor binding site, an epitope sensitive to a loss of the glycan at N332 and distinct from that recognized by the bNAb 2G12 and an epitope sensitive to an I165A substitution. In approximately half of the donors, key N-linked glycans were critical for expression of the epitopes recognized by the bNAb specificities in the sera
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